Apparatus for shifting the phase of an electrical current



Sept. 16, 1958 M. soRKlN 2,852,733

APPARATUS ECR SHIFTING THE PHASE 0F AN ELECTRICAL CURRENT Filed June 10, 1954 2 Sheets- Sheet 1 6 BY 'l 7 j AT] R l NEYS Sept. 16, 1958 M. soRKlN 2,852,733

APPARATUS FOR SHIF'TING THE PHASE OF AN ELECTRICAL CURRENTl Filed June l0, 1954 2 Sheets-Shea*l 2 TJCVEL l BY ugabvm A ORNEYS APPARATUS FR SHiFTiNG THE PHASE F AN ELECTRICAL CURRENT Morris Sorkin, New York, N. Y., 'assigner to Reeves Instrument Corporation, New York, N. Y., a corporation of New York Application June l0, 1954, Serial No. 435,719

7 Claims. (Cl. 323-109) The present invention relates-to an inductive phase shifter and relates, more particularly, to an apparatus for effecting an electrical phase shift in response to rotation of a shaft.

An object of the present invention is to provide an inductive phase shifter in which the use of brushes and slip rings or the like is eliminated. The elimination of brushes provides complete freedom from electrical noise and disturbance due to sliding electrical contact. Another object of the invention is to provide an inductive phase shifter by means of which greatly increased accuracy and linearity of the phase shift may be attained. Another object of the invention is to provide an inductive phase shifter which may be operated over a wide frequency range and at frequencies in the radio frequency region.

Another object of the invention is the provision of an inductive phase shifter wherein the electrical phase shift is twice the angular displacement of the shaft. In this way the shaft rotation required for a given rate of change in phase is, of course, reduced and increases the speed at which a desired phase shift may be obtained.

A further object of the invention is to provide an inductive phase shifter in which the associate circuit components may be rapidly and accurately adjusted for maximum accuracy.

Still another object of the invention is a new and improved structure for inductive phase Shifters that is characterized by its simplicity, low cost and relatively high eiciency.

The above and other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming part of this application.

In the drawings:

Fig. l is a schematic circuit diagram for an inductive phase shifter embodying the present invention;

Fig. 2 is a schematic circuit diagram illustrating a different form of a phase shifter embodying the invention;

Fig. 3 is a cross sectional view of an inductive phase shifter embodying the present invetion;

Fig. 4 is an exploded view in perspective of the eld structures of the phase shifter shown in Fig. 3;

Fig. 5 is a perspective view of the shields used in the phase shifter shown in Fig. 3; and

Fig. 6 is a diagrammatic illustration of the stator windings for the phase shifter shown in Fig. 3.

Basically, an inductive phase shifter embodying the invention comprises a pair of stator windings inductively yisolated one from the other and a rotor assembly inductively coupled to each stator. Thus, the relative phase of a voltage applied to one stator and the voltage induced into the second stator is a function of the angular position of the rotor forming the coupling therebetween.

As is shown diagrammatically in Fig. l, there is an input stator 10 consisting of two windings 11 and 12 which are mechanically 90 degrees apart and an output stator 13 consisting of two windings 14 and 15 which are like Wise mechanically 90 degrees apart. The input and Patented Sept. 16, 1953 ice output stators 10 and 13 are inductively isolated from each other, but each of the stators is inductively coupled to a common rotor winding 16 which is rotatable relative thereto.

The junction points 17 and 18 of the windings on the respective stators 10 and 13 are connected to a common ground bus 19. The windings 11 and 12 on the input stator 10 are connected, respectively, to input terminals 20 and 21. The bus 19 is connected to an input terminal 22 and an output terminal 24. The winding 14 of the output stator 13 is connected Ito an output terminal 23 through a condenser 25 and the other winding 15 thereon is connected to the output terminal 23 through a resistance 26, The ends of the rotor winding 16 are connected together and this winding thus forms a closed loop.

When a voltage EI cos (wt) is applied to the input terminal 20 and a voltage E, sin (wt) is applied to input terminal 21, an output voltage EO==EIK1KO sin (wt-Ido) is obtained at the output terminal 23 where: KI and KO are constants and qb is the angle of rotation of the rotor relative to the stators. In other words, the phase of the output voltage will shift relative to the phases of the input voltages by an amount equal to 2o.

In Fig. 2, components corresponding to those of Fig. 1 bear like numbers with a prime thereafter, In this figure, input voltages E1 cos (wt) and EI sin (wt) are applied to the windings 11 and 12', respectively, of the input stator 10 from a single source of voltage applied between the input terminals 20 and 22 by connecting a capacitor 27 in series with the stator winding 11 and a resistor 28 in series with the stator winding 12' and the input terminal 20. The values of capacitor 27 and the resistor 28 are selected so that they represent approximately constant current sources for the winding 11 and 12', respectively, and they thus produce a phase difference of approximately in the voltages applied to the two windings. The values of the capacitor 27 and the resistor 28 may also be `adjusted so that the currents in the respective stator windings are equal at a desired frequency.

The winding 15 of the output stator 13 is connected to the output terminal 23 through a capacitor 29 and the winding 14 thereof is connected to the output terminal 23 through a resistor 30 with the capacitor and the resistor being arranged as described above.

In order to enable the utilization of this device at frequencies. within the radio frequency range and of the order of kc. or higher, the currents in the stator windings should be determined by the resistors and capacitors alone and the only coupling between the rotor and each stator should be purely inductive. To achieve this result, all of the stator and rotor windings are electrostatically shielded one from the others by the shields S (shown in dotted outline in Fig. 2), which are independently connected to the ground bus 19.

In order to obtain accuracy of phase shift corresponding to the angular displacement or rotation of the rotor, it is necessary to adjust the voltages and currents in the windings accurately in magnitude and phase. This may be simplified by positioning the output stator windings 90 degrees away from the corresponding input stator windings and skewing the rotor windings with a skew of unity. rThis permits the input and output resistors and condensers to be adjusted independently to establish equal output voltages at relative rotor positions of =0, 90, and 270.

In addition to the foregoing adjustments, the electrical phase angle of the input and output voltages can be further adjusted for rotor positions =90 and 270 or the corresponding electrical phase angles of 6=l80 and 540.. This may be accomplished by means of an auxiliary variable condenser 31 connected between stator windings 15 and ground. The value of the condenser 31 is adjusted while observing a trace on an oscilloscope when the input voltage is applied to the horizontal deflection plates of the oscilloscope and the output voltage to the vertical deflection plates of the oscilloscope. The condenser 31 is properly adjusted when the trace on the screen of the scope will be at 135 for electrical phases of =180 and 540 and at 45 line for electrical phases of 0:0", 360 and 720.

Figs. 3 to 6, inclusive, illustrate the structure of an inductive phase shifter embodying the invention. In these figures, the input and output stators 33a and 33b, respectively, correspond to the stators and 13 of Figs. 1 and 2, and the rotor 34 corresponds to the rotor V16. The rotor 34 and the stators 33a and A33b are wholly contained within an outer cylindrical housing 35 having a side wall 36 and a fixed end wall 37. One end 38 of the armature shaft 38 is rotatably mounted in a bearing 39 secured to the end wall 37 and extends beyond the wall for attachment to driving apparatus. The other end 38 of the shaft 38 is supported by a bearing 40, mounted 'in the opposing end wall 41 threadably secured to the side Wall 36 of the housing 35 by threads 42. The entire housing is then closed by a face plate 43.

The stators 33a and 33b surround the rotor 34 and are held in alignment within the housing 35 by a circular spacing member 44 of T-shaped section and a pair of circular end members 45 and 46. The end member 4S constitutes in etect part of the removable end plate 41, while the end member 46, of L-shaped section, rests at against the xed wall 37 of the housing 35. In this way insertion of the end wall 41 secures the entire assembly including the stators and the rotor in position.

Referring now to the stators 33a and 33b which are identical in structure, each comprises a core or ring 47 of magnetic material having a plurality of radially spaced transverse slots or channels 48. Each of the slots 48 has a narrow opening 49 on the inner side and form a plurality of stator pole pieces 50 (see Fig. 3). The slots accommodate two sets of field windings 51 and 52 which are mechanically 90 apart and are separated by two sets of shields 53 and 54 of which one set 53 is shown in perspective in Fig. 5.

Considering the windings 51 and 52, each of which comprise a plurality of turns in each of the slots 48 and form wound and installed in the usual manner, a diagrammatic View of the disposition of these windings is shown in Fig. 6. The winding 51 which is disposed in the bottom of the slots 48 is illustrated by generally horizontal heavy solid and dotted lines terminating in a pair of lead wires 55 and 56. In practice, these leads 55 and 56 are shielded by a suitable metal covering as illustrated at 57 in Fig. 4. The second winding 52 is represented by substantially vertical dotted and solid lines of lighter weight and lies in the bottom of the slots 48. The lead wires for this winding are denoted by the numerals 58 and 59 which are included within the shielded cable 60 of Fig. 4. The corresponding connecting cables of stator 33b are denoted by the numerals 61 and 62.

As pointed out above, it is important to electrostatically shield these windings one from the other and from the rotor 34 and this is accomplished by two sets of circular shields 53 and 54, which are substantially identical except for diameter.

As shown in Fig. 5, the shield 53 consists of two rings 53a and 53b, each of which has a multiplicity of tabs 63 that tit into the slots 48 in the core 47 and are split, as denoted at 64, to prevent the generation of circulating currents therein. When the rings 53a and 53b are inserted in the winding, as shown in Fig. 3, the opposing tabs 63 are held in spaced relationship as shown at 65 and the external parts of the rings extend outwardly beyond the windings at the ends of the stator. The anged portionor rib 44 of the central metallic spacer 44 functions to shield the stators one from the other and in order to prevent any possibility of the shield sets 53 and 54 from touching the shield part 44', the latter is provided with flanking insulating rings 66. With this arrangement the windings of both stators are completely shielded one from the others and from the rotor.

The cables 61 and 62 of the stator 33b are brought out of the housing through openings in the center shielding rib 44 of spacer 44 and appropriate openings in the stator core 33a as shown in Fig. 4. Thus all four sets of lead wires may be brought out the same end of the housing. The shields 53a and b and 54a and b are grounded by separate ground leads 67 connected to the shields at points opposite to the slots 64 as shown in Figs. 4 and 6.

The rotor 34 is constructed along the lines of the stators 33a and 33b in that it includes a number of longitudinal slots 68 for reception of a winding 69. This winding is short circuited so that currents induced therein by one stator will set up a field and thereby induce currents into the other stator as described in connection with Figs. l and 2. In addition, the slots 68 are skewed at a proper pitch (unity) relative to the axis of rotation of rotor 34 in order to achieve the desired phase angle between the currents in the two stators.

The structure shown in Figs. 3 and 4 corresponds to the electromagnetic elements of Figs. l and 2 and does not include the resistors and condensers shown therein. Such components may be enclosed in a separate cornp'artment or compartments formed as part of the housing 35 or may constitute separate structures for interconnection with the windings of the stators.

The embodiment of the invention as described above will function at frequencies of the order of kc. and even higher and rotation of the shaft 38, will produce an electrical phase shift corresponding to twice the angle of rotation of the shaft. In addition, either of the stators may serve as an input stator `and the other the output stator.

While only certain embodiments of the invention have been shown -and described, it is apparent that changes, alterations, Iand modications may be made without departing from the true scope and spirit thereof.

I claim:

1. An inductive coupling device comprising in combination an elongated housing having a longitudinal axis, a pair of annular magnetic stators coaxially mounted within said housing about said longitudinal axis and being longitudinally spaced apart, each of said stators having a plurality of circumferentially distributed winding receiving slots, a pair of similar windings disposedl on each of s'aid stators, said windings consisting of a plurality of turns of insulated wire situated within the slots of Isaid stators, the axis of electrical symmetry of one of said pair of windings on each stator being spaced 90 from the axis of electrical symmetry of the other winding on each stator, a laminated magnetic rotor coaxially situated within said stators and supported for rotation about said longitudinal axis, said rotor including a plurality of circumferentially -distributed winding receiving slots, a single closed-loop winding consisting of a plurality of turns of insulated wire wound about an axis perpendicular to said longitudinal axis and disposed within slots of said rotor, said closed-loop winding mutually coupling the pair of windings on one of said stators with the pair of windings on the other stator, the mutual coupling between each of said pair of stator windings and said closed-loop rotor winding varying according to the angular position of said rotor about said longitudinal axis.

2. The inductive coupling device as defined in claim 1 further comprising means adapted for supplying first and second alternating voltages in phase quadrature to the pair of similar windings on yone of said stators, and phaseshifting means combining the induced output voltages from the pair of similar windings on said other stator, the phase of the output voltage from said phase-shifting means varying with respect to the phase of one of the applied alternating voltages according to the angular position of said rotor.

3. The inductive coupling device as dened by claim l further comprising an annular magnetic shield situated between said pair of stators and coaxilly surrounding said longitudinal :axis for preventing inductive coupling between said stators.

4. An inductive coupling device comprising in cornbination an elongated housing having a longitudinal axis, a pair of annular stators coaxially mounted within said housing 'about said longitudinal axis and being longitudinally spaced apart, each of said annular stators having a polyphase winding thereon, and a rotor coaxially situated Within said pair of annular stators and supported for rotation about said longitudinal axis, said rotor having a single closed-loop winding, said single closed-loop winding consisting of a plurality of turns of wire wound about an axis perpendicular to said longitudinal axis, one end of said winding being directly coupled to the other end, said closed-loop winding being inductively coupled to both of said polyphase stator windings, the inductive coupling between said closed-loop winding and each of said stator windings varying according to the angular position of said rotor about said longitudinal axis.

5. An inductive coupling device comprising in combination a pair of stators coaxially mounted about a longitudinal axis and being longitudinally spaced apart, each of said stators having a polyphase winding thereon, and a single closed-loop rotor winding situated within said pair of stators and supported for rotation about said longitudinal axis', said single closed-loop winding consisting of a plurality of turns of wire wound about a second axis intersecting said longitudinal axis, one end of said winding being directly coupled to the other end, said closedloop winding being inductively coupled to both of said pair of polyphase stator windings, the axis of electrical symmetry of said closed-loop rotor Winding being rotatable about said longitudinal axis for varying the inductive coupling between said closed-loop winding and each of said stator windings according to the angular position of said rotor winding about said longitudinal axis.

6. A rotatable phase-shifting device comprising in combination, an inductive coupling device including an elongated housing having a longitudinal axis, a pair of stators coaxially mounted within said housing about said longitudinal axis and being longitudinally spaced apart, each of said stators having a polyphase Winding thereon, a rotor coaxially situated within said stators and supported for rotation about said longitudinal axis, said -rotor having la single closed-loop winding, said single closed-loop winding consisting of 'a plurality of turns of wire Wound about an axis perpendicular to said longitudinal axis, one end of said winding being directly coupled to the other end, said closed-loop winding being y inductively coupled to both. of said polyphase stator windings, the inductive coupling between said closed-loop winding and each of said stator windings varying according to the angular position of said rotor about said longitudinal axis, means adapted for supplying polyphase alternating voltages to one of said polyphase windings, and a phase-shifting network coupled to the other polyphase winding for combining the induced alternating output voltages from said other polyphase winding, the phase of the output voltage from said phase-shifting network varying with respect to one of the applied polyphase voltages according to the angular position of said rotor.

7. A rotatable phase-shifting device comprising in combination, an inductive coupling device having a pair of annular stators coaxially mounted about a longitudinal axis and being longitudinally spaced apart, each of said annular stators having a polyphase Winding thereon, a single closed-loop rotor winding situated within said annular stators and supported for rotation about said longitudinal axis, said single closed-loop winding consisting of a plurality of turns of wire Wound about a second axis intersecting said longitudinal axis, one end of said winding being directly coupled to 'the other end, said closedloop winding being inductively coupled to both of said pair of polyphase stator windings, the axis of electrical symmetry of said closed-loop Winding being rotatable about said longitudinal axis for varying the inductive coupling between said closed-loop winding and each of said stator windings according to the angular position of said rotor winding about said longitudinal axis, a rst phase-shifting network coupled to one of said polyphase windings, said lirst phase-shifting network being adapted for receiving an applied alternating voltage and supplying polyphase voltages to said one polyphase winding, and a second phase-shifting network coupled to the other polyphase winding for combining the alternating voltages induced in ysaid other polyphase winding, the phase of the output voltage from said second phase-shifting network varying with respect to the phase of an applied alternating voltage to said first phase-shifting network according to the angular position of said rotor.

References Cited in the lile of this patent UNITED STATES PATENTS 1,353,145 Clement Sept. 21, 1920 1,673,673 Girault lune 12, 1928 1,897,415 Barbour Feb. 14, 1933 2,174,017 Sullinger Sept. 26, 1939 2,442,097 Seeley May 25, 1948 2,496,920 Seeley Feb. 7, 1950 2,608,682 Herr Aug. 26, 1952 2,627,598 Browder et al. Feb. 3, 1953 2,660,681 Horne Nov. 24, 1953 FOREIGN PATENTS 660,064 Great Britain 0st.. 31, 1951 

